The present invention relates to fuses, and more particularly to an under oil expulsion fuse cartridge assembly.
Under oil expulsion fuses are generally used in high voltage systems to protect the electrical devices from fault currents. An expulsion fuse can be used by itself or in tandem with backup current limiting fuses since it can be used to provide current interruption under low fault conditions without operation of the more costly limiting fuse.
State of the art expulsion fuse cartridges are typically manufactured by assemblying two brass end contacts such that their projecting annular lips surround opposite ends of a molded nylon sleeve, winding a glass filament epoxy strengthening layer over the nylon sleeve and projecting lips, and then coating the epoxy layer with an arc extinguishing material such as polyester until the outer surface of the polyester is flush with the outer surface of the brass end contacts. A replaceable fuse assembly is inserted within the sleeve and is held in position by a pair of clamping nuts threaded into the outer ends of the two end contacts.
One problem with such an assembly is that when the clamping nuts are turned down into the end contacts to engage the ends of the fuse link they may break the fuse link due to the applied forces. It is therefore desirable to provide means for preventing direct contact or engagement of the clamping nut with the end of the fuse link and yet maintain adequate electrical contact therewith. It has also been found desirable to provide a fuse link which will open during overload conditions at a predetermined temperature and location.